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Fitting a Chuck to a Rotary Table

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PeterB14/07/2010 17:30:46
14 forum posts
Is there any relatively easy way I can fit a 3-jaw chuck concentrically to a rotary table when the chuck only has mounting holes from the rear.  Or do I have to go out and buy one with mounting holes from the front?  
The table has a 3MT taper in the centre.  
Regards to All, Peter
Norman Barber14/07/2010 18:01:51
14 forum posts
If your chuck has a Myford backplate you can buy an adaptor which fits your rotary table and has a Myford threaded nose to accept the chuck.  Alternatively you can do what I have done and make an adaptor which fits the MT in the table and has a threaded nose to suit whatever is on the chuck backplate.  If you do this you must use a drawbar to secure the adaptor in the table taper - it is a very short taper.
Norman Barber
AndyB14/07/2010 18:06:01
167 forum posts
7 photos
Hi Peter,
I am just in the process of doing the same.
I have got a three-slot table so could make a backplate to fit the table, mounting with T nuts and bolts and bolting the chuck to this backplate first.
Chronos sell these for their rotary tables...where I got the idea from. You just make your own.
To make it more versatile (because I want to use other tooling as well) I am making an arbour threaded with the spindle nose uppermost and an MT taper to fit the table (mine's MT2) so that I can screw any of my chucks to the arbour.
I forget where I got this idea from, just to say it's not mine.
JasonB14/07/2010 19:22:41
15164 forum posts
1548 photos
John (Bogstandard) did a good write up on making a suitable mounting
If its not a threaded chuck then turn a circular plate about 25mm larger dia than the chuck, counterbore or countersink for the chuck mounting screws and then mill 3 or 4 slots into the edge depending on the number of slots in your table and use these with tee nuts, studs etc to hold it to your table just like the Chronos ones
Ramon Wilson14/07/2010 22:28:45
674 forum posts
72 photos
I use a 4" 3 Jaw in this fashion regularly.
I have a 3/8 thick 5" dia. 'sub plate' that has a short male register turned on one side to locate in the RT and a female register on the top side that accepts a plug to register the chuck concentrically. The chuck was drilled for 6mm capheads that hold it to the sub plate (from beneath), the sub plate is then held to RT with 6mm capheads into tee nuts in the RT slots
I should add that the 3 jaw is the Myford type with internal thread and register which makes the above relatively straight forward. This will of course be more of a problem if the chuck has a conventional backplate.
In the near future I'm intending to make a low profile indexing table and intend to drill right through the chuck for the hold down bolts. This will eliminate the sub plate.
Hope this helps as well
Regards - Ramon

Edited By Ramon Wilson on 14/07/2010 22:31:48

Stewart Hart15/07/2010 06:31:03
591 forum posts
294 photos
This is how I did it for a rear three cap screw clamping chuck  system.
peter walton15/07/2010 08:55:55
82 forum posts
Only problem with all these designs is that the whole stack is getting a bit on the high side which so reduces the work that can be done under the mill.
One just cannot win, what we need is a thinner chuck better still one built into a rotab!
Ian S C15/07/2010 11:54:47
7300 forum posts
228 photos
I made a threaded nose with a 100mm dia flange with slots to take bolts that go into T nuts in my 6" rotary table, I,v tryed to keep things as low as possible, but with 8" chucks I have minimal room with the jacobs chuck in the mill, so I find use for short drills ect.Ian S C
Richard Parsons15/07/2010 13:34:43
645 forum posts
33 photos

Your chuck must be either larger or smaller than your rotary table.

I chose a 3” (76mm) chuck whose body was smaller than my 4” (100mm) rotary table.

Here is how I did it.

  1. I took a lump of 3/8” (10mm) plate bigger than my table and centred it in my 4 Jaw
  2. I drilled and reamed a ½” (12.5mm) hole right through it. This will be needed later.
  3. I machined a hollow about 1/8” (3.2 mm) deep to be a nice fit over my rotary table.
  4. Reverse the plate in the 4 jaw holding it from inside the hollow you have just machined using ½” hole to centre it accurately.
  5. Bring up a tail stock centre to stop anything jumping out of the chuck
  6. Machine the outside of the plate to bring it round.
  7. Machine the face to form a stub about 1/8” long which is a snug fit into back of the chuck you are going to use.
  8. Remove the work piece
  9. Next make a small mandrel to fit into ½” hole and into the chucks own back plate.
  10. Use this to line your  the chuck’s own back plate and your new adaptor and spot through the retaining screws to hold the chuck to the adaptor. Use counter sunk screws.
  11. Finally mark drill and fit the hold down screws into the slots on the table.

I would attach a picture but Windows Vista is still playing up (Comeback NT4 ALL is forgiven). Windows software updates are not released they escape


Stub Mandrel15/07/2010 21:36:03
4306 forum posts
291 photos
On my home made table I made a small table the same diameter as the mini-lathe chuck (80mm) with a deep groove all round so you can get at the mounting screws. It means its a bit higher than usual by about 1", but I can also put my 7" faceplate on it.
You should be able to see a bit of it in this picture:

Speedy Builder516/07/2010 12:01:19
1711 forum posts
118 photos
I suppose you could make a short locating plug, MT one end, and some sort of boss to fit the chuck at the other end.  Then hold the chuck down using Tee nuts and long bolts/ clamps on the outside of the chuck.  This would give you maximum vertical headroom.  Drill/ bore a hole thro the plug in case you need to mount a longer workpiece in the chuck.  Bit crude,  but it would work !
PeterB16/07/2010 17:01:48
14 forum posts
I go away for a couple of days and there are a myriad of really helpful replies.  Thank you so much!  I will be able to make a suitable chuck fitting for my RT this weekend.   
For what its worth my chuck is a Chinese one with a shallow recess for fitting to a backplate.  Unfortunately, no Myford or Boxford here.  So I'll be using the ideas based on the thick plate twixt RT and Chuck.  
It is indeed interesting that none of the usual tool suppliers has filled the requirement for an RT with an integral, concentric, low-height chuck over a wide range of sizes....
Oh and Bogstandard/John/Madmodder now has a new fan.  
Thanks again to all who replied.
Ian Parkin16/07/2010 18:24:26
606 forum posts
166 photos
The way I get it concentric  is place my morse taper test bar in the hole in the RT
then place the chuck over it
clamp the jaws onto the test bar then bolt the chuck down
undo jaws and knock the test bar out

Edited By Ian Parkin on 16/07/2010 18:27:09

Michael Edwards 106/12/2018 17:46:51
15 forum posts
6 photos

I have the adaptor from Chronos for the Boxford lathe and mount it to my rotary table Only issue I have is that it often unwinds itself so I need to come up with some idea to fix it when trying to machine a large flywheel as the lathe will not take the size of flywheel. Any body have any ideas?? Newbie Mike

Clive Foster06/12/2018 18:07:54
1664 forum posts
46 photos

Need some sort of brake clamp on the chuck.

Could make some brake shoe devices to bolt into the rotary table slots and come into firm contact with the body of the chuck. Need one in each slot to ensure force is symmetrical so no tendency for the chuck to be pushed out of true. I'd use softwood shoes on an L shaped bracket with a projection on the base of the L so that tightening the bolt pushes the shoe into contact. Use a scrap of alloy sheet under the projection so it doesn't mark the table.

Simpler way would be to get one of the long jubilee clips used to hold smoke deflectors on chimneys, central heating pressure vessels (and probably lots of other things) to clamp simple L brackets to the chuck which could similarly be bolder to the table. 3 mm alloy would probably work, bends easily and will take up the chuck diameter when the clip is done up. Maybe two clips for extra security.


Michael Edwards 106/12/2018 18:51:19
15 forum posts
6 photos

Thank you Clive I will look into that

Joseph Noci 106/12/2018 20:06:44
458 forum posts
812 photos

Hi Peter,

a week or so ago I posted a bit on my rotary table fitted with a chuck. I made a base-plate (photo below, right) between chuck and table- The base plate bolts to the table and is larger in diameter than the table and chuck. I drilled the chuck through so that it bolts onto the base plate from the front of the chuck.

Surrounding the chuck is a larger ring that also bolts to the base plate ( below left) and has four screws through the side that impinge on the chuck. Backing off slightly on the three chuck bolts allows the work piece to be nicely centred using the 4 side screws, and then tighten up the chuck bolts.

Forgive the repeat of the photos of the previous post - I have not managed to work out how to give a link to just a specific section post in the forum...

centering ring complete with backplate.jpg

adjusting screws.jpg

ring lathe work done.jpg

rotary table on mill table.jpg

John Haine06/12/2018 22:14:31
2454 forum posts
132 photos

I have drilled 4 M10 holes in my RT allowing me to bolt down a 4 jaw chuck. They were carefully located to make the chuck body as near concentric as possible. But the way I look at it is that I would never put something round in the 3 jaw in the lathe and expect it to run true - I always try to plan to get all the concentric things turned at one setting. If something has to run true it goes in the 4 jaw on the lathe. So why is it different on a rotary table?

Simon Collier07/12/2018 00:44:28
283 forum posts
51 photos

I used the threaded holes in the chuck body to fit studs and bolted it to the RT using round nuts with radial tommy bar holes to bolt to the slots. Clocked the chuck true and tightened. I have a 6" RT for non- chuck use. img_0080.jpg

not done it yet07/12/2018 07:05:10
2807 forum posts
11 photos

JH has it in a nutshell. A four jaw independent chuck is the way to go. No chuck alignment needed, just centre the workpiece.

Thought proceess might be best started with the RT purchase - four T-slots, not three. I mistakenly bought a 4 jaw self centering chuck for mine and regretted it. I will change it for an independent four jaw next time I need to remove it. The independent chuck does not even need to be mounted that central - how many rotary tables are spun at high speed!

A baseplate fitted to a three slotted RT, followed by the 4 jaw chuck is better than a self centering chuck. I cringed, every time I have wanted to remove that current chuck, to mount something direct on the RT. It will not be fitted centrally again!

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